Connectors for signal and/or power transmission refer generally to connecting devices designed for use with electronic signals and/or electric power, and their accessories. These connectors can be viewed as bridges for all kinds of signals, and their quality affects the stability of signal and/or current transmission and is crucial to the operation of electronic systems. With the advancement of electronic technology, such connectors have had different specifications and developed into various models that vary in their fields of application, physical dimensions, and methods of use, in addition to the types of the signals to be transmitted. For all the specifications and models, however, “transmission stability” and “durability” have always been two major factors that cannot be overlooked in connector design.
Take a “cable connector” for connecting with a coaxial cable for example. A coaxial cable typically has a central conductor, either single-core (e.g., a single bare copper wire) or multicore (e.g., a twisted pair of copper wires, a copper-clad steel wire, or a tin-plated copper wire), surrounded sequentially by layers of tubular materials. More specifically, the conductor is surrounded by an insulation layer; the insulation layer, by a copper braid shield (generally made of a mesh of copper, aluminum, or other metal wires); and the copper braid shield, by a jacket (made of an insulating plastic material). Having a concentric cross section, coaxial cables are structured to shield the electromagnetic signals transmitted therethrough from the interference of external noise and are therefore often used to transmit high-frequency signals such as video and network signals.
Generally speaking, referring to FIG. 1, a cable connector uses its signal terminal 11 and ground terminal 12 to clamp a coaxial cable 10 (please note that the housing and other irrelevant components of the cable connector are not shown in FIG. 1). More particularly, the signal terminal 11 clamps one end of the coaxial cable 10 and cuts through the exposed insulation layer 101 in order to be electrically connected to the conductor inside. The ground terminal 12, on the other hand, cuts through the jacket 102 of the coaxial cable 10 and is electrically connected to the copper braid shield. Ideally, signal transmission through the coaxial cable 10 generates an evenly distributed electromagnetic field that fluctuates only when the cable is extended to an interface whose impedance is different from that of the cable. In other words, the electromagnetic field is changed only at the junctures between the coaxial cable 10, the signal terminal 11 (or the ground terminal 12), and the circuit board 13 due to the differences in impedance between the aforesaid components. This change in electromagnetic field nevertheless causes unstable signal transmission. To minimize the negative impact of such a mismatch in impedance, the distance 110 between the signal terminal 11 and the ground terminal 12 should be as short as possible.
However, with the copper braid shield of the coaxial cable 10 having relatively low structural strength, reducing the distance 110 between the signal terminal 11 and the ground terminal 12 requires that the ground terminal 12 clamp the copper braid shield at a position adjacent to the edge of the copper braid shield, thus compromising the clamping strength between the ground terminal 12 and the copper braid shield; that is to say, when the coaxial cable 10 is pulled, the copper braid shield is very likely to be torn, and the coaxial cable 10 may get loose as a result.
But if the distance 110 between the signal terminal 11 and the ground terminal 12 is increased to enable the ground terminal 12 to clamp the main body (i.e., the portion with a denser structure than the edge) of the copper braid shield, the electromagnetic field generated by signal transmission will reflect between the signal terminal 11 and the ground terminal 12, thereby aggravating the negative impact of the mismatch, or discontinuity, of impedance. A cable connector designer, therefore, must decide between “transmission stability” (i.e., to shorten the distance 110 between the signal terminal 11 and the ground terminal 12) and “durability” (i.e., to increase the distance 110 between the signal terminal 11 and the ground terminal 12) and cannot achieve both. The issue to be addressed by the present invention is to resolve the dilemma by improving the structure of the conventional cable connectors.